November 24, 2012

Sometimes a morning sky can be a combination of serene and surreal. Such a sky perhaps existed before sunrise as viewed from a snowy slope in eastern Switzerland. Quiet clouds blanket the above scene, lit from beneath by lights from the village of Trübbach. A snow covered mountain, Mittlerspitz, poses dramatically on the upper left, hovering over the small town of Balzers, Liechtenstein far below. Peaks from the Alps can be seen across the far right, just below the freshly rising Sun. Visible on the upper right are the crescent Moon and the bright planet Venus. Venus will remain in the morning sky all month, although it will likely not be found in such a photogenic setting.

Four of the first ALMA antennas at the Array Operations Site (AOS), located at 5000 metres altitude on the Chajnantor plateau, in the II Region of Chile. Three of them — those which are pointing in the same direction — are being tested together as part of the ongoing Commissioning and Science Verification process. Across the image in the background is the impressive plane of the Milky Way, our own galaxy, here seen looking toward the centre. The centre of our galaxy is visible as a yellowish bulge crossed by dark lanes. The dark lanes are huge clouds of interstellar dust that lie in the disc of the galaxy. While opaque in visible light, they are transparent at longer wavelengths, such as the millimetre and submillimetre radiation detected by ALMA. ALMA, the Atacama Large Millimeter/submillimeter Array, is the largest astronomical project in existence and is a truly global partnership between the scientific communities of East Asia, Europe and North America with Chile. ESO is the European partner in ALMA.

November 23, 2012

The limb of the Earth is a work of beauty and a gift to science. When observed from space, the layers of the atmosphere remind us of the fragility of the cocoon that shelters life. That same view also allows scientists to detect the gases and particles that make up the different layers of our atmosphere. Astronauts aboard the International Space Station captured a bit of both in this digital photograph from July 31, 2011. They threw in the Moon as an extra gift.

Closest to Earth’s surface, the orange-red glow reveals the troposphere—the lowest, densest layer of atmosphere, and the one we live within. A brown transitional layer marks the upper edge of the troposphere, known as the tropopause. A milky white and gray layer rests above that, likely a slice of the stratosphere with perhaps some noctilucent clouds in the mix. The upper reaches of the atmosphere—the mesosphere, thermosphere, and exosphere—fade from shades of blue to the blackness of space.

The different colors occur because the dominant gases and particles in each layer act as prisms, filtering out certain colors of light. Instruments carried on satellites and on craft such as the space shuttle have allowed scientists to decipher characteristics of the ozone layer and the climate-altering effects of aerosols.

A thin crescent of the Moon is illuminated by the Sun from below the horizon of the Earth. Though the Moon is more than 384,400 kilometers (238,855 miles) away, the perspective from the camera makes it appear to be part of our atmosphere.

From an altitude of over 5,000 meters, the night sky view from Chajnantor Plateau in the Chilean Andes is breathtaking in more ways than one. The dark site's rarefied atmosphere, at about 50 percent sea level pressure, is also extremely dry. That makes it ideal for the Atacama Large Millimeter/submillimeter Array (ALMA) designed to explore the Universe at wavelengths over 1,000 times longer than visible light. Near the center of the the panoramic scene, ALMA's 7 and 12 meter wide dish antennas are illuminated by a young Moon nestled in the arc of the Milky Way. ALMA's antenna configurations are intended to achieve a resolution comparable to space telescopes by operating as an interferometer. At left, a meteor's streak and the Milky Way's satellite galaxies, the Large (bottom) and Small Magellanic Clouds grace the night.

What kind of cloud is this? A roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud. When this happens uniformly along an extended front, a roll cloud may form. Roll clouds may actually have air circulating along the long horizontal axis of the cloud. A roll cloud is not thought to be able to morph into a tornado. Unlike a similar shelf cloud, a roll cloud, a type of Arcus cloud, is completely detached from their parent cumulonimbus cloud. This a roll cloud extends far into the distance in 2009 January above Las Olas Beach in Maldonado, Uruguay.

November 22, 2012

This colour image of the region known as NGC 2264 — an area of sky that includes the sparkling blue baubles of the Christmas Tree star cluster and the Cone Nebula — was created from data taken through four different filters (B, V, R and H-alpha) with the Wide Field Imager at ESO's La Silla Observatory, 2400 m high in the Atacama Desert of Chile in the foothills of the Andes. The image shows a region of space about 30 light-years across.

A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

This object, called the Helix nebula, lies 650 light-years away, in the constellation of Aquarius. Also known by the catalog number NGC 7293, it is a typical example of a class of objects called planetary nebulae. Discovered in the 18th century, these cosmic works of art were erroneously named for their resemblance to gas-giant planets.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun. These stars spend most of their lives turning hydrogen into helium in massive runaway nuclear fusion reactions in their cores. In fact, this process of fusion provides all the light and heat that we get from our sun. Our sun will blossom into a planetary nebula when it dies in about five billion years.

When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

The glow from planetary nebulae is particularly intriguing as it appears surprisingly similar across a broad swath of the spectrum, from ultraviolet to infrared. The Helix remains recognizable at any of these wavelengths, but the combination shown here highlights some subtle differences.

The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in yellow A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

The brighter purple circle in the very center is the combined ultraviolet and infrared glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust was most likely kicked up by comets that survived the death of their star.

Before the star died, its comets, and possibly planets, would have orbited the star in an orderly fashion. When the star ran out of hydrogen to burn, and blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, kicking up an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded.

Infrared data from Spitzer for the central nebula is rendered in green (wavelengths of 3.6 to 4.5 microns) and red (8 to 24 microns), with WISE data covering the outer areas in green (3.4 to 4.5 microns) and red (12 to 22 microns). Ultraviolet data from GALEX appears as blue (0.15 to 2.3 microns).

November 21, 2012

Are those UFOs near that mountain? No - they are multilayered lenticular clouds. Moist air forced to flow upward around mountain tops can create lenticular clouds. Water droplets condense from moist air cooled below the dew point, and clouds are opaque groups of water droplets. Waves in the air that would normally be seen horizontally can then be seen vertically, by the different levels where clouds form. On some days the city of Seattle, Washington, USA, is treated to an unusual sky show when lenticular clouds form near Mt. Rainier, a large mountain that looms just under 100 kilometers southeast of the city. This image of a spectacular cluster of lenticular clouds was taken in December 2008.

What's visible in the night sky on this picture? To help illustrate the answer, a beautiful land, cloud and skyscape was captured in February 2011 over Neuchâtel, Switzerland. Visible in the foreground were the snow covered cliffs of the amphitheater shaped Creux du Van, as well as distant trees, and town-lit clouds. Visible in the night sky were galaxies including the long arch of the central band of our Milky Way Galaxy, the Andromeda galaxy (M31), and the Triangulum galaxy (M33). Star clusters visible included NGC 752, M34, M35, M41, the double cluster, and the Beehive (M44). Nebulas visible included the Orion Nebula (M42), NGC 7822, IC 1396, the Rosette Nebula, the Flaming Star Nebula, the California Nebula, the Heart and Soul Nebulas, and the Pacman Nebula.

November 20, 2012

Astronomers announced they can now predict with certainty the next major cosmic event to affect our Galaxy, Sun, and Solar System: the titanic collision of our Milky Way Galaxy with the neighboring Andromeda Galaxy

The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the Sun will be flung into a new region of our Galaxy, but our Earth and Solar System are in no danger of being destroyed.

The solution came through painstaking NASA Hubble Space Telescope measurements of the motion of Andromeda, which also is known as M31. The galaxy is now 2.5 million light-years away, but it is inexorably falling toward the Milky Way under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both.

The scenario is like a baseball batter watching an oncoming fastball. Although Andromeda is approaching us more than two thousand times faster, it will take four billion years before the strike.

Computer simulations derived from Hubble's data show that it will take an additional two billion years after the encounter for the interacting galaxies to completely merge under the tug of gravity and reshape into a single elliptical galaxy similar to the kind commonly seen in the local Universe

Although the galaxies will plow into each other, stars inside each galaxy are so far apart that they will not collide with other stars during the encounter. However, the stars will be thrown into different orbits around the new galactic center. Simulations show that our solar system will probably be tossed much farther from the galactic core than it is today.

To make matters more complicated, M31's small companion, the Triangulum galaxy, M33, will join in the collision and perhaps later merge with the M31/Milky Way pair. There is a small chance that M33 will hit the Milky Way first.

The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope's deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.

A century ago astronomers did not realize that M31 was a separate galaxy far beyond the stars of the Milky Way. Edwin Hubble measured its vast distance by uncovering a variable star that served as a "milepost marker."

Edwin Hubble went on to discover the expanding universe where galaxies are rushing away from us, but it has long been known that M31 is moving toward the Milky Way at about 250,000 miles per hour. That is fast enough to travel from here to the Moon in one hour. The measurement was made using the Doppler Effect, which is a change in frequency and wavelength of waves produced by a moving source relative to an observer, to measure how starlight in the galaxy has been compressed by Andromeda's motion toward us.

Previously, it was unknown whether the far-future encounter will be a miss, glancing blow, or head-on smashup. This depends on M31's tangential motion. Until now, astronomers have not been able to measure M31's sideways motion in the sky, despite attempts dating back more than a century. The Hubble Space Telescope team, led by van der Marel, conducted extraordinarily precise observations of the sideways motion of M31 that remove any doubt that it is destined to collide and merge with the Milky Way.

Atmospheric gases scatter blue wavelengths of visible light more than other wavelengths, giving the Earth’s visible edge a blue halo. At higher and higher altitudes, the atmosphere becomes so thin that it essentially ceases to exist. Gradually, the atmospheric halo fades into the blackness of space. This astronaut photograph captured on July 20, 2006, shows a nearly translucent Moon emerging from behind the halo.

Technically, there is no absolute dividing line between the Earth’s atmosphere and space, but for scientists studying the balance of incoming and outgoing energy on the Earth, it is conceptually useful to think of the altitude at about 100 kilometers above the Earth as the “top of the atmosphere.” The top of the atmosphere is the bottom line of Earth’s energy budget, the Grand Central Station of radiation. It is the place where solar energy (mostly visible light) enters the Earth system and where both reflected light and invisible, thermal radiation from the Sun-warmed Earth exit. The balance between incoming and outgoing energy at the top of the atmosphere determines the Earth’s average temperature. The ability of greenhouses gases to change the balance by reducing how much thermal energy exits is what global warming is all about.

Greenhouse gases aren’t the only part of the Earth system that influence the energy balance. The percent of incoming sunlight the Earth system reflects (the Earth’s albedo) is a key climate factor since whatever is reflected can’t go on to warm the planet. Clouds, such as those blanketed the earth int he image above, snow, and ice have the biggest influence on how reflective Earth is. When any of these factors change, Earth’albedo can change. Since the late 1990s, NASA satellites have been observing the top of the atmosphere with sensors known as CERES, short for “Clouds and the Earth’s Radiant Energy System,” and scientists have been using the data to look for signs of change in the amount of energy the Earth reflects or emits.

Because snow and ice are so reflective, scientists have long expected that melting of snow and ice in the polar regions will accelerate climate warming by reducing the Earth’ albedo. Atmospheric scientist Seiji Kato of NASA’s Langley Research Center and several teammates have used a suite of NASA and NOAA (National Oceanic and Atmospheric Administration) satellite observations to investigate whether this feedback is already underway. The team compared reflected sunlight, clouds, and sea ice and snow cover at polar latitudes from 2000-2004. What they found was a bit of a surprise: while snow and ice in the Arctic declined, the albedo didn’t change.

The Sun erupted with two prominence eruptions, one after the other over a four-hour period on November 16, 2012, between the hours of 1 and 5 a.m. EST. The red-glowing looped material is plasma, a hot gas made of electrically charged hydrogen and helium. The prominence plasma flows along a tangled and twisted structure of magnetic fields generated by the sun’s internal dynamo. An erupting prominence occurs when such a structure becomes unstable and bursts outward, releasing the plasma.

The action was captured by NASA's Solar Dynamic Observatory (SDO) in the 304 Angstrom wavelength of extreme ultraviolet light. The expanding particle clouds heading into space do not appear to be Earth-directed.

NASA engineer Ernie Wright looks on as the first six flight ready James Webb Space Telescope's primary mirror segments are prepped to begin final cryogenic testing at NASA's Marshall Space Flight Center.

This represents the first six of 18 segments that will form NASA's James Webb Space Telescope's primary mirror for space observations. Engineers began final round-the-clock cryogenic testing to confirm that the mirrors will respond as expected to the extreme temperatures of space prior to integration into the telescope's permanent housing structure.

The James Webb Space Telescope (sometimes called JWST) will be a large infrared telescope with a 6.5-meter primary mirror. The project is working to a 2018 launch date

November 18, 2012

Sometimes, if you wait long enough for a clear and moonless night, the stars will come out with a vengeance. One such occasion occurred earlier June, 2012 at the Piton de l'Eau on Reunion Island. In the foreground, surrounded by bushes and trees, lies a water filled volcanic crater serenely reflecting starlight. A careful inspection near the image center will locate Piton des Neiges, the highest peak on the island, situated several kilometers away. In the background, high above the lake, shines the light of hundreds of stars, most of which are within 100 light years, right in our stellar neighborhood. Far in the distance, arching majesticallyoverhead, is the central band of our home Milky Way Galaxy, shining by the light of millions of stars each located typically thousands of light years away. Theastrophotographer reports waiting for nearly two years for the sky and clouds to be just right to get this shot.

ESO Photo Ambassador, Babak Tafreshi has captured an outstanding image of the sky over ESO’s Paranal Observatory, with a treasury of deep-sky objects.

The most obvious of these is the Carina Nebula, glowing intensely red in the middle of the image. The Carina Nebula lies in the constellation of Carina (The Keel), about 7500 light-years from Earth. This cloud of glowing gas and dust is the brightest nebula in the sky and contains several of the brightest and most massive stars known in the Milky Way, such as Eta Carinae. The Carina Nebula is a perfect test-bed for astronomers to unveil the mysteries of the violent birth and death of massive stars.

Below the Carina Nebula, we see the Wishing Well Cluster (NGC 3532). This open cluster of young stars was named because, through a telescope’s eyepiece, it looks like a handful of silver coins twinkling at the bottom of a wishing well. Further to the right, we find the Lambda Centauri Nebula (IC 2944), a cloud of glowing hydrogen and newborn stars which is sometimes nicknamed the Running Chicken Nebula, from a bird-like shape that some people see in its brightest region. Above this nebula and slightly to the left we find the Southern Pleiades (IC 2632), an open cluster of stars that is similar to its more familiar northern namesake.

In the foreground, we see three of the four Auxiliary Telescopes (ATs) of the Very Large Telescope Interferometer (VLTI). Using the VLTI, the ATs — or the VLT’s 8.2-metre Unit Telescopes — can be used together as a single giant telescope which can see finer details than would be possible with the individual telescopes. The VLTI has been used for a broad range of research including the study of circumstellar discs around young stellar objects and of active galactic nuclei, one of the most energetic and mysterious phenomena in the Universe.